"PITCH TEST (revised 5/25): It's somewhat unusual to find significant pitch errors in today's digital audio players. And, if the error is consistent sample-to-sample, it's likely a design error with the hardware or firmware. There's already some info on the web about the Clip+ "running fast" and mine indeed does but only by a very small amount: 0.25%. So the musical note Middle C is 441 hz instead of 440 hz. I wonder how many would notice this, but I did confirm the problem using my Agilent bench meter (which has an extremely accurate internal timebase) and playing back a "perfect" 1 Khz sine wave:

ROCKBOX PITCH FIX: The good folks who maintain Rockbox apparently knew about the above error, and interestingly, fixed it in their firmware. Here's the same Clip+ playing the same file but running Rockbox and the error is now near zero (0.04%):"